The Miraculous Blood of Horseshoe Crab

When I was young I was baffled to see blue-colored blood squirting out from the chest of Broly, the antagonist in the Japanese anime Dragon Ball, after he was sent hurling towards the sun by Goku and sons. 

So I thought having blue-blood was one of the characteristics of alien races.

Most animals have red blood. Our blood is red thanks to the presence of iron (Fe) in our hemoglobin. Hemoglobin transports oxygen, and since oxygen has poor solubility in water, iron is needed to bind those oxygen molecules onto the hemoglobin.

But some animals have blue-colored blood. In fact they are so common some of them often end up on our dining table. The octopus and squid, along with the humble Horseshoe Crab have blue blood, thanks to the presence of copper as oxygen-transporting agent in their blood, and the blue-colored copper-based molecules are called hemocyanin. 

Image: cccmkc.edu.hk

Scientists have found out that the blue blood of Horseshoe Crabs does miraculous thing: when a crab gets injured and its insides are exposed to invading bacteria, a particular blood cell explodes, sending a mass of blood-clotting granules that instantly block out the invaders. Our blood clot too, thanks to the platelets in our blood. 

Frederick Bang first discovered the awesome quality of the Horseshoe Crab's blood in the 1950s. He realized that the blood could serve as an alarm system to protect products (human cells, DNA) from contamination, as the blood clot as soon as there is any sign of negative bacteria. He isolated the clotting agent and called it Limilus amoebocyte lystate (LAL), and a quart of this LAL could cost up to $15,000. A high-profit investment indeed. 

Image: oar.noaa.gov

Fishermen would harvest crabs, extract their blood, sell the serum to pharmaceutical companies, and return the crabs to the wild. But not all crabs survive the ordeal--3~15% of the crabs die after being bled. As a result, the population of Horseshoe Crab in some states in the U.S has dropped significantly.

Image: pbs.org

The Horseshoe Crab is one of the oldest creatures to ever walked the Earth. It has outlived the dinosaurs, and has had millions of years to perfect its defense system against invisible enemies. We seek to "borrow" their blood for our own interest, so it would be a shame if we fail keep the species alive in the end.

Malcolm

info: 

http://www.npr.org/blogs/krulwich/2012/05/31/154095868/what-the-vampire-said-to-the-horseshoe-crab-your-blood-is-blue

http://www.essortment.com/horseshoe-crabs-miracle-blood-41662.html

http://www.austincc.edu/~emeyerth/hemoglob.htm